CN121157462A - Preparation methods and applications of fully biodegradable washable nonwoven fabrics - Google Patents

Abstract

This invention provides a method for preparing a fully degradable, washable nonwoven fabric, comprising: S10: forming a washable first base layer and a second base layer, and stacking the first base layer and the second base layer, wherein the first base layer and the second base layer include PLA fibers; S20: impacting the first base layer with a pulsed hot airflow to form micropores, thereby causing at least a portion of the PLA fibers in the first base layer to bond with the fibers in the second base layer. The washable nonwoven fabric formed by the above method can meet the balance between strength and washability and can meet the composting biodegradability requirements in ISO 14855. This invention also provides a fully degradable, washable nonwoven fabric prepared using the above preparation method.

Description

Preparation method and application of fully-degradable flushable non-woven fabric

Technical Field

The invention relates to a flushable non-woven fabric.

Background

The flushable non-woven fabric is taken as a material which gives consideration to the convenience of modern life and the environmental protection, and has great application prospect in various fields such as wet tissues, sanitary products, medical dressings and the like. The core technical challenge is to meet the strength and toughness required in the production and use processes, and ensure that the product can be rapidly and thoroughly dispersed in water after being used, so that the drainage system is prevented from being blocked. These two performance indicators, strength and flushable capability, present a significant and difficult-to-reconcile inherent contradiction in materials science and engineering practice.

Because the strength is directly related to the basis weight, the currently widely used flushable non-woven fabric is usually 45-75g/m2 for better balance strength and flushable capacity, but people hope that the flushable non-woven fabric is applied to wider occasions, such as face tissues or wiping tissues, and further hope that the flushable non-woven fabric has thicker thickness, and the more direct means for increasing the thickness is to increase the basis weight, for example, the basis weight is increased to above 90 g/m2, so that more satisfactory thick feeling can be obtained, but the strength is directly increased when the basis weight is increased, so that the dispersing performance is difficult to meet the requirement.

In the document CN120867009a, it is proposed that a fluffy weakened structure is formed by a structural reconstruction manner, that is, by a region corresponding to a secondary drying-induced wetting point, and a fluffy structure is induced by local accurate wetting and secondary drying, so that a high basis weight flushable non-woven fabric with a weight of more than 85g/m2 can be used for maintaining the strength of the non-woven fabric and achieving the rapid dispersion capability, but in this manner, a high-precision lattice spray liquid is required to be used, more specifically, an expensive piezoelectricity spray head is required to be used and a high-precision vision system is combined to achieve the high-precision spray liquid, so that the equipment investment and maintenance cost are greatly increased.

In the other document CN116121954a, a multilayer structure and a flushable nonwoven fabric having good dispersibility and strength are obtained by punching a second mixed web and injecting a hydrosol into the holes and combining the first mixed web and the third mixed web, but this method requires additional punching work and fixing with a hydrosol, increases the number of steps, introduces a hydrosol work, and causes inconvenience in production.

In addition, the existing flushable non-woven fabric is difficult to meet the requirements of the composting biodegradation rate in ISO 14855, and therefore, a new technical scheme is needed to solve the technical problems.

Disclosure of Invention

A preparation method of a fully-degradable flushable non-woven fabric comprises the following steps:

S10, forming a first base layer and a second base layer which can be scattered, and overlapping the first base layer and the second base layer, wherein the first base layer and the second base layer comprise PLA fibers;

And S20, impacting the first base layer through pulse hot air flow to form micropores and bonding at least part of PLA fibers in the first base layer with fibers of the second base layer.

In one embodiment, in step S10, the first base layer or the second base layer is formed by:

S101, providing a fiber raw material.

The fiber raw materials comprise 60-70% of wood pulp fibers, 20-33% of viscose fibers and 5-15% of PLA fibers by mass, wherein the length of the PLA fibers is 4-12 mm, the fineness of the PLA fibers is 1.5-3.0 denier, and the melting point of the PLA fibers is 165-175 ℃;

s102, forming a fiber into a net;

S103, water thorn reinforcement;

and S104, drying and forming a base layer, wherein the drying temperature is controlled within the range of 80-140 ℃ and the drying time is 0.5-5 min during drying.

In one embodiment, the cross-sectional shape of the PLA fiber is trilobal, and the PLA fiber has a curled shape with a curl number of 8-15/25 mm.

In one embodiment, in step S101, the fiber raw material further includes a hot-melt fiber, where the content of the hot-melt fiber in the fiber raw material is 0.5-3.0%, the hot-melt fiber is an ES fiber with a sheath-core structure, the core layer is a polyester PET or a polypropylene PP, the sheath layer is a low-melting-point polymer, and the melting point of the sheath layer is 140-150 ℃.

In one embodiment, in step S20, the temperature of the pulsed hot gas flow is 160 ℃ to 180 ℃.

In one embodiment, in step S20, the impact pressure of the pulsed hot air flow on the first substrate is 0.3 to 0.6 MPa, and the pulse impact time is 0.05 to 0.2 seconds.

In one embodiment, in step S20, micropores are formed with a diameter of 0.1 to 0.5 mm.

In one embodiment, the distribution density of the micropores on the first base layer is 1 to 2 micropores/cm 2.

In one embodiment, the basis weights of the first base layer and the second base layer are the same, and the basis weights of the first base layer and the second base layer are less than 40g/m2.

The invention also provides the fully-degradable flushable non-woven fabric prepared by the preparation method.

The preparation method of the fully-degradable flushable non-woven fabric has the beneficial effects that S10, a first base layer and a second base layer which can be flushable are formed, the first base layer and the second base layer are overlapped, the first base layer and the second base layer comprise PLA fibers, S20, the first base layer is impacted by pulse hot air flow to form micropores, at least part of PLA fibers in the first base layer are combined with fibers of the second base layer, and the flushable non-woven fabric formed by the method can meet the balance of strength and flushable and meet the requirement of composting biodegradation rate in ISO 14855.

Drawings

FIG. 1 is a schematic diagram of a fully degradable flushable nonwoven fabric structure according to an embodiment of the present invention;

illustration of the elements:

A substrate 10, a first base layer 11, micropores 111, and a second base layer 12.

Detailed Description

The embodiment of the invention provides a flushable non-woven fabric, which is characterized by comprising the following steps of:

s10, forming a first base layer 11 and a second base layer 12 which can be scattered, and stacking the first base layer 11 and the second base layer 12, wherein the first base layer 11 and the second base layer 12 comprise PLA fibers.

In this embodiment, the first base layer 11 and the second base layer 12 may be formed as follows:

S101, providing a fiber raw material.

The fiber raw materials comprise 60% -70%, 20% -33% and 5% -15% of wood pulp fibers, viscose fibers and polylactic acid short fibers (PLA fibers).

The wood pulp fiber is a softwood pulp fiber with the length of 2.0-4.5 mm, preferably, the average fiber length of the softwood pulp fiber is 2.5 mm-3.7 mm, so that the flushable non-woven fabric has enough strength and meets flushable requirements through the higher water dispersibility and longer length of the softwood pulp fiber, and meanwhile, when the softwood pulp fiber is adopted, the freeness of the formed softwood pulp is preferably 200-700 cc, and the freeness is measured by a Canadian standard freeness measuring method.

The viscose fiber comprises round viscose fiber and flat viscose fiber, the proportion of the viscose fiber in the fiber mixture is 20% -33%, the proportion of the round viscose fiber is 15% -20%, and the proportion of the flat viscose fiber is 5% -13%, it can be understood that the flat viscose fiber can be obtained by dissolving natural fiber in corresponding solvent and then spinning by wet method, compared with the round viscose fiber, the flat viscose fiber has smaller bending rigidity and is more easy to be entangled, generally, the fibers in the first base layer 11 or the second base layer 12 can be entangled by virtue of the physical properties of the fibers, and the entanglement is a friction cohesion effect, and because the flat viscose fiber can be entangled by using less external force than the round viscose fiber, the flat viscose fiber is more easy to be dispersed in water than the round viscose fiber.

In the embodiment, the round viscose fiber has the length of 4-20 mm, the denier of 1-3, the length-diameter ratio of more than or equal to 3000, the entanglement strength and the softness are provided by the round viscose fiber, and in one specific embodiment, the round viscose fiber with the length of 6mm, 12mm or 18mm can be used.

The length of the flat viscose fiber is 5-15 mm, the denier is 0.5-2, and the length-diameter ratio is more than or equal to 4000, so that the flat section is easy to deform in water flow, and the dispersibility is enhanced.

Preferably, the width-to-thickness ratio of the flat viscose fiber is more than or equal to 2:1, the width-to-thickness ratio of the flat viscose fiber is more preferably 2.5:1-4:1, and the dispersibility and the softness can be improved on the premise of ensuring sufficient wet strength.

The viscose fiber can be lyocell fiber, the length range of the viscose fiber is 8-15 mm, the linear density is controlled to be 1.2-1.8 denier, and the proportion is 20-40%. The lyocell fiber has excellent wet strength and biodegradability, and contributes to improvement of the flushable property of a product, and it can be understood that the length is an average length and the linear density is an average linear density.

In this embodiment, the length of the PLA fiber is 4-12 mm, so that the PLA fiber can form effective mechanical entanglement in the fiber network, providing basic dry/wet strength for the nonwoven fabric, and preventing the fiber from being too long, resulting in uneven dispersion and flocculation in wet-laid, affecting the uniformity of the laid fabric, and further damaging the uniformity and the dispersion performance of the base layer.

Furthermore, the fineness of PLA fiber is 1.5~3.0 denier to on the one hand guarantee that single fiber has sufficient rigidity and intensity, can effectively puncture in the pulse hot air current and get into another basic unit, form firm juncture, on the other hand, avoid the fibre too thick to lead to stiff, the softness decline of feeling, too thick fibre is difficult to break when dashing simultaneously, is unfavorable for fast disintegration.

Further, the cross section of the PLA fiber is round or trilobal, the PLA fiber has a curled shape, the number of curls is 8-15/25 mm, preferably, the cross section of the PLA fiber is trilobal, the friction force and cohesion force between the fibers are increased through the special-shaped cross section of the trilobal, and the strength of the fiber web is enhanced under the condition that no additional adhesive is used. Meanwhile, the special corner structures are easier to concentrate stress when being subjected to water flow shearing force, so that the disintegration of a fiber network is accelerated, and meanwhile, the PLA fibers have a curled form, so that the fluffiness and entanglement capacity of the fibers can be greatly improved, and the formed non-woven fabric is softer and more elastic. Under the action of the pulse hot air flow, the curled PLA fibers can be hooked with each other like a spring, so that a firmer interlayer combination structure is formed.

Further, the melting point of the PLA fiber is 165-175 ℃ so as to be matched with the temperature of the pulse hot air flow at 160-180 ℃, namely the temperature of the pulse hot air flow is precisely controlled in a range slightly higher than the melting point of the PLA but far lower than the decomposition temperature of wood pulp/viscose fiber, so that only the PLA fiber is locally melted, precise interlayer thermal bonding is realized, and the hydrophilic cellulose fiber skeleton is kept complete, thereby ensuring excellent flushability of the final product.

In addition, it was found in research that, on the one hand, polylactic acid staple fibers have a higher modulus (i.e., stiffer) than wet cellulose fibers, and form a composite structure with extremely soft flat viscose fibers in a base layer, and the rigid peripheral winding flexible tape, polylactic acid staple fibers can provide better support for the skeleton of wood pulp fibers, preventing the nonwoven fabric from excessively stretching and deforming in use, while flat viscose fibers serve as filling and buffering materials, so that the durability and toughness of the nonwoven fabric are jointly improved, on the other hand, when the flushable nonwoven fabric is flushed into a toilet bowl and enters a sewer, under the mechanical action and the microbial action of water flow, polylactic acid staple fibers start to hydrolyze, molecular chains thereof break, fiber strength gradually decreases, and at the same time, the volume slightly swells, internal stress is generated at fiber winding nodes, and when the water flow acts, the polylactic acid staple fibers break more easily or fall off from the entanglement, so that the disintegration process of the whole fiber network is greatly accelerated.

Further, in order to improve the interface combination of the polylactic acid short fiber and the hydrophilic cellulose fiber, the polylactic acid short fiber can be subjected to surface hydrophilization pretreatment, such as normal pressure plasma treatment, or hydrophilic masterbatch with the concentration of 0.5-1.5% is blended in the spinning process.

Furthermore, the fiber raw material is also added with 1% -3% by mass of water-soluble adhesive, such as carboxymethyl cellulose (CMC) or modified polyvinyl alcohol (PVA), so as to compensate the strength loss introduced by PLA, and the adhesive is preferably pH-responsive, such as citric acid crosslinked PVA with 5% -10% of crosslinking degree, so as to maintain the strength when in use and dissolve rapidly when in flushing.

Further, the fiber raw material further comprises a hot-melt fiber, wherein the hot-melt fiber is used for providing more hot-melt bonding points in the heating process of the pulse air flow, so that the bonding strength between the two layers is ensured, the content of the hot-melt fiber in the fiber raw material is 0.5-3.0%, the hot-melt fiber is preferably ES fiber with a sheath-core structure, the core layer is specifically a high-melting-point polymer, specifically a polyester PET or polypropylene PP, the sheath layer is a low-melting-point polymer, specifically a polyethylene PE or modified copolyester, and the melting point of the sheath layer is preferably 140-150 ℃ so as to form more hot-melt bonding points when the melting point of the PLA fiber is slightly lower than that of the pulse air flow, and the temperature of the sheath layer is matched with that of the pulse air flow.

In addition, the fineness of the hot-melt fiber is 1.5-3.0 denier so as to prevent the too coarse fiber from affecting the softness and dispersibility of the material while providing enough bonding points, and the length is 4-8 mm so as to ensure that the hot-melt fiber has good dispersibility in wet-laid and cannot flocculate.

S102, forming a fiber into a net.

The fiber-forming process may employ wet-laid. In the process of forming the fiber web, the basis weight of the fiber web is controlled to be in the range of 35-65 grams per square meter, and the forming speed is maintained to be 50-200 meters per minute.

Further, the fiber forming may be performed by a wire former comprising a headbox and a forming wire, said forming wire being configured in endless loop form and being supported for movement by a number of carrier rolls, said carrier rolls comprising breast rolls located upstream of the headbox, a portion of said forming wire downstream of the breast rolls being arranged obliquely upwards relative to the horizontal, a section of which is referred to as a forming section, the headbox applying a mixed stock of fiber stock onto the forming section from above, and dewatering the stock into a wet fiber web.

S103, water thorn reinforcement.

Specifically, the wet fiber web may be subjected to hydroentangling reinforcement by means of a hydroentangling unit comprising a plurality of hydroentangling modules arranged in sequence along the running direction of the wet fiber web, preferably, the plurality of hydroentangling modules comprising a pre-needling module, a main needling module and a micro-needling module.

The pre-needling assembly is used for carrying out preliminary compaction and entanglement on the wet fiber web, wherein the pre-needling assembly comprises 1-2 hydroentangled heads, the hydroentangled pressure is 20-30 Bar, and spraying is carried out from top to bottom on the wet fiber web during hydroentangled.

The main needling assembly is used for enabling fibers to be subjected to severe displacement, penetration, bending and entanglement, so that a main network structure is formed, wherein the main needling assembly comprises 3-5 hydroentangled heads, the hydroentangled pressure is 50-80 Bar, and meanwhile, the hydroentangled heads of the main needling assembly can be arranged on the upper side and the lower side of a wet fiber web so as to spray from the upper side and the lower side of the wet fiber web simultaneously.

The micro-needling assembly is used for carrying out entanglement and finishing on the surface and the inside of a fiber web through ultra-high pressure and ultra-fine water so as to carry out micro-adjustment and surface finish treatment on the wet fiber web through micro-needling, the micro-needling assembly comprises a micro-needling water needle plate, the micro-needling water needle plate comprises holes with the diameter of 0.08-0.1 mm, the water pressure is 100-130 Bar when micro-needling is carried out, the micro-needling assembly can penetrate deep into the fiber web through high-energy micro-needles in the micro-needling process, fibers which are not completely entangled after main needling and particularly in the middle part are fixed, in addition, fiber hairiness generated on the surface of the fiber web in the steps of pre-needling and main needling can be eliminated through micro-needling, so that the surface of the material is smooth and flat, the hand feeling is improved, the phenomenon of falling of powder is avoided, and the structure can be optimized through micro-needling, namely the fluffy structure and the pore structure of the fiber web are optimized, and the strength, the softness and the dispersibility of the material are balanced.

And S104, drying and forming a base layer.

The drying temperature is controlled within the range of 80-140 ℃ during drying, the drying time is 0.5-5 min, the final water content is reduced to below 8%, and it can be understood that the drying temperature is controlled below 140 ℃, so that PLA fibers can be prevented from being hot-melted to form internal bonding points to cause difficult dispersion, and meanwhile, when the hot-melt fibers are arranged, part of the hot-melt fibers are softened to form a small number of bonding points to increase strength.

It is understood that the first base layer 11 and the second base layer 12 are laminated with the row base 10 after the first base layer 11 and the second base layer 12 are formed.

And S20, impacting the first base layer 11 through the pulse hot air flow to form micropores 111 and bonding at least part of PLA fibers in the first base layer 11 with fibers of the second base layer 12.

It will be appreciated that the pulsed hot air flow is needle-shaped to impact the first substrate 11 in a manner facing the substrate 10, and during the impact process, the stiffer and relatively coarser PLA fibers soften and bend under the action of the pulsed hot air flow and bend and turn along the impact direction of the pulsed hot air flow, and under the action of the pulsed hot air flow, at least a portion of the PLA fibers enter the second substrate 12 and form bonds with the fibers in the second substrate 12, where the bonds are the PLA fibers cooled and thermally fused to the fibers in the second substrate 12.

It can be understood that under the action of the pulse hot air flow, the micro holes 111 penetrating the first base layer 11 are formed in the area of the first base layer 11 corresponding to the pulse hot air flow, the air permeability of the layer of the base 10 is increased by the micro holes 111, and on the other hand, during the process of flushing, water flow can easily enter into the base 10 through the micro holes 111, further can enter into the interface between the first base layer 11 and the second base layer 12 along the micro holes 111, and enter into the second base layer 12, so that the first base layer 11 and the second base layer 12 are easily separated during the flushing, and the first base layer 11 and the second base layer 12 are independently flushed.

It will be appreciated that the depth to which the PLA fibers in the first substrate 11 are softened into the second substrate 12 can also be controlled by adjusting the impact strength of the pulsed hot gas flow, thereby meeting the different use requirements of the substrate 10.

Further, the temperature of the pulse hot air flow is 160 ℃ to 180 ℃, so that the temperature of the pulse hot air flow is just above the melting point of the PLA fiber, but is not too high, and excessive melting of the PLA fiber caused by the pulse hot air flow is avoided, so that excessive bonding among fibers in the first base layer 11 is avoided, and the fibers are difficult to disperse.

Further, the impact pressure of the pulse hot air flow to the first base layer 11 is 0.3-0.6 MPa, and the pulse impact time is 0.05-0.2 seconds.

Further, the diameter of the formed micropores 111 is 0.1-0.5 mm, so that on one hand, rapid water flow permeation and disintegration are facilitated, on the other hand, obvious difference between the first base layer 11 and the second base layer 12 is avoided, and large strength difference between the first base layer 11 and the second base layer 12 is prevented, so that layering phenomenon is avoided in the use process.

Further, the distribution density of the micro holes 111 on the first base layer 11 is 1 to 2 micro holes/cm 2, so as to avoid the excessive bonding strength between the first base layer 11 and the second base layer 12.

Further, the basis weights of the first base layer 11 and the second base layer 12 are the same, and the basis weights of the first base layer 11 and the second base layer 12 are less than 40g/m2.

The invention also provides the fully-degradable flushable non-woven fabric using the preparation method.

The flushable nonwoven fabric of the present invention is further described below by way of examples.

Examples

The first base layer comprises 65% of wood pulp fibers, 24% of viscose fibers, 10% of PLA fibers and 1% of hot melt fibers;

wherein, the length of PLA fiber is 8mm, the fineness is 2.0 denier, the cross section is trilobal, the number of curls is 12/25 mm, and the melting point is 170 ℃.

The heat-melting fiber comprises an ES fiber, a sheath-core structure, a sheath layer of polyethylene PE with a melting point of 145 ℃, a core layer of polyester PET with a fineness of 2.0 denier and a length of 6mm.

Basis weight 45g/m2.

The second base layer is identical to the first base layer.

The temperature of the hot air flow is 175 ℃.

Impact pressure 0.4 MPa.

Pulse impact time 0.1 seconds.

The air flow is needle-shaped and is opposite to the surface of the basal body, the pore diameter of the micropores is 0.5mm.

Comparative example 1

The flushable nonwoven fabric shown in CN109537168 a.

The matrix comprises 65% of softwood pulp fibers (average length 3.0 mm), 30% of round viscose fibers (length 12mm, denier 2 denier), 5% of flat viscose fibers (length 8mm, denier 1.5 denier, width-thickness ratio 2:1) and basis weight of 90 g/m2.

The microprotrusions are uniformly distributed on the surface of the whole non-woven fabric, the density is 20/25 mm < 2 >, the diameter is 0.4mm, and the height is 0.4mm.

	Unit (B)	Example 1	Comparative example 1
				Basis weight	g/m2	90	90
Water dispersibility	s	301	577
				MDT	N/m	791	810
MDT-wet	N/m	173	163
				CDT	N/m	317	391
Biodegradability of the material	%	90	73

The testing method comprises the following steps:

Water dispersibility Using INDA/EDANA FG502 Specification (Shake box method, 2L water, 22.+ -. 3 ℃ C., 33 rpm), the nonwoven disintegration time (first tablet separation) was recorded.

And (3) tensile force test:

dry tensile (MDT and CDT) referring to GB/T24218.3-2010, sample width 50 mm, grip spacing 100mm, draw speed 100 mm/min, and results expressed in N/m.

Wet tensile (MDT-wet): referring to GB/T12914-2008, sample width 50mm, grip spacing 50mm, stretching speed 100 mm/min, and results are expressed in N/m.

Biodegradability-reference is made to ISO 14855 (standard composting conditions, 90 day degradation rate).

From the test results, the method provided by the invention can balance strength and flushable performance, and meets the requirement that the degradation rate in ISO 14855 is more than or equal to 90% in 90 days.

The foregoing description is only of embodiments of the present invention, and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes using the descriptions and the drawings of the present invention or directly or indirectly applied to other related technical fields are included in the scope of the present invention.

Claims (10)

1. The preparation method of the fully-degradable flushable non-woven fabric is characterized by comprising the following steps of:

S10, forming a first base layer and a second base layer which can be scattered, and overlapping the first base layer and the second base layer, wherein the first base layer and the second base layer comprise PLA fibers;

And S20, impacting the first base layer through pulse hot air flow to form micropores and bonding at least part of PLA fibers in the first base layer with fibers of the second base layer.

2. The method of manufacturing according to claim 1, wherein in step S10, the first base layer or the second base layer is formed by:

s101, providing a fiber raw material;

The fiber raw materials comprise 60-70% of wood pulp fibers, 20-33% of viscose fibers and 5-15% of PLA fibers by mass, wherein the length of the PLA fibers is 4-12 mm, the fineness of the PLA fibers is 1.5-3.0 denier, and the melting point of the PLA fibers is 165-175 ℃;

s102, forming a fiber into a net;

S103, water thorn reinforcement;

and S104, drying and forming a base layer, wherein the drying temperature is controlled within the range of 80-140 ℃ and the drying time is 0.5-5 min during drying.

3. The preparation method according to claim 2, wherein the PLA fiber has a trilobal cross-sectional shape, and the PLA fiber has a curl form, and the number of curls is 8 to 15/25 mm.

4. The method of claim 3, wherein in step S101, the fiber raw material further includes a hot-melt fiber, the content of the hot-melt fiber in the fiber raw material is 0.5-3.0%, the hot-melt fiber is an ES fiber with a sheath-core structure, the core layer is polyester PET or polypropylene PP, the sheath layer is a low-melting polymer, and the melting point of the sheath layer is 140-150 ℃.

5. The method according to claim 4, wherein in the step S20, the temperature of the pulse hot air is 160-180 ℃.

6. The method according to claim 5, wherein in step S20, the impulse pressure of the impulse hot air flow to the first substrate is 0.3-0.6 MPa and the impulse time is 0.05-0.2 seconds.

7. The method according to claim 6, wherein in step S20, the micropores are formed with a diameter of 0.1 to 0.5 mm.

8. The method of claim 7, wherein the distribution density of micropores on the first substrate is 1 to 2 micropores/cm 2.

9. The method of making according to claim 8 wherein the first substrate and the second substrate have the same basis weight and the first substrate and the second substrate have a basis weight of less than 40g/m2.

10. A fully degradable flushable nonwoven fabric prepared by the method of claim 1.